The increasing awareness of the importance of sterility in hypodermic devices has led to the development of disposable syringes. The initial sterility of these devices, coupled with their low cost, has led to their widespread use in preference to reusable devices requiring sterilization before reuse. But this widespread use of disposable syringes has created problems. By their economic nature, inexpensive devices, utilized in high numbers, tend to make inventory controls on new and used devices difficult and prone to breakdown. It is not uncommon for syringes, along with the attached needles, to find their way into unauthorized hands. Once control is lost, these devices may be reused without sterilization.
Reuse of hypodermic syringes, intended for a single use only, is an important factor in the transfer of contagious diseases and facilitation of drug abuse. Intravenous drug users who routinely share and reuse syringes are a high risk group with respect to HIV and the hepatitis virus. Easy access to the devices further facilitates illegal drug use. In addition, the effects of repeated uses of syringe products may be responsible for the spread of many other diseases.
One solution to these problems is to develop syringes which functionally self-destruct after a single application. While the availability of non-reusable syringes will not necessarily stop illegal drug use, it can prevent sharing of contaminated hypodermic syringes and thus help reduce the spread of diseases.
Many approaches have been made to prevent and limit reuse. Initially, syringe designs incorporated features facilitating an explicit destructive act. Thus, by the application of force, the syringe became inoperable. Other designs included special structures to lock the device in a position preventing reuse. Some designs utilized locks incorporated in the barrel section of the syringe, requiring full extension to engage the device. Other designs require the syringe to be prefilled, and do not allow filling of the syringe in the conventional manner. Additional designs required multiple parts and careful assembly. Further, many of these designs relate to syringes which can be rendered inoperable after a single use, rather than syringes which are automatically rendered inoperable by the act of using the syringe a first time. Thus, the safety features may be easily defeated by an unscrupulous user who wishes to reuse the syringe.
The ideal syringe design would incorporate a locking mechanism that would allow conventional use of the syringe (e.g., normal filling operations). In addition, the design would be simple to operate, not requiring any special training. The design should be able to utilize standard hypodermic needles. The design should be inexpensive and reliable and should encourage the full and complete elimination of valuable medication. Finally, the design should automatically render the syringe inoperable for a second use after it is used in a conventional manner on its first use.